Prolactin is an essential hormone for reproduction in mammals. The neuroendocrine mechanisms which govern the secretion of prolactin are only partialy understood. Prolactin releasing factors (PRFs) and release-inhibiting factors (PIFs) are secreted by the hypothalamus into hypophyseal portal blood and act directly at the putuitary level to control the rate of prolactin release. In addition, there are a number of brain neuropeptides which act, in large part, via indirect mechanisms to induce prolactin secretion. These neuropeptides are present in relatively high concentrations with the hypothalmus of rats and are viewed as potentially important links between the physiologic stimuli which evoke prolactin release and the secretion of PIFs and PRFs into hypophyseal portal blood. The purpose of the proposed study is to determine how neuropeptides stimulate the release of prolactin from the rat pituitary gland, and then to attempt to integrate the prolactin-releasing actions of neuropeptides with those of neurotransmitters. I plan to accomplish these objectives first by measuring changes in the secretion rates of hypophysiotropic agents induced by neuropeptide treatment. Having established how each of five neuropeptides affects the secretion of three hypophysiotropic agents, I will then utilize specific blockers of histamine and serototin action to determine whether these aminergic neurotransmitters mediate the effects of neuropeptides on the secretion of PIF and PRFs into hypophseal protal blood. The proposed studies will provide valuable information toward our understanding of prolactin regulatory processed in particular, and of neuroendocrine integration in general. Moreover, this knowledge can eventually be used for identifying the causes of, and developing treatments for, pathologies of prolactin secretion in humans such as lactational insufficiency and galactorrhea-amenorrhea.